Wireless contention reduction

ABSTRACT

The subject disclosure relates to a computer-implemented method for reducing access contention in a wireless medium. In some aspects, a method of the technology includes steps for exchanging data packets with multiple client devices in a wireless network, and based on the data exchange, identifying a first device from among the multiple client devices for which one or more higher-layer (e.g., Layer 3 and/or Layer 4) packets are likely to be received. In some aspects, a method of the technology can further include steps for broadcasting a lower-layer (e.g., Layer 2) packet to the plurality of client devices, wherein the lower-layer packet includes an extended duration field to suppress transmission by one or more listening client devices until at least one subsequent higher-layer packet is received from the first device. Systems and machine-readable media are also provided.

BACKGROUND 1. Technical Field

The subject technology provides solutions for reducing contention in awireless network, and in particular for reducing wireless contentioncaused during exchange of Layer 3 and Layer 4 acknowledgement traffic.

2. Introduction

Many wireless local area network (WLAN) deployments are based upon theIEEE 802.11 standards that provide protocols to enable access betweenmobile devices, and to other networks, such as hard-wired local area andglobal networks, such as the Internet. In receiving Internet data, acommon gateway operating in a conventional IP/TCP protocol may beutilized. The IEEE 802.11 architecture is comprised of severalcomponents and services that interact to provide station mobilitytransparent to higher layers of the network stack. IEEE 802.11 basednetworks define stations as components that connect to a wireless mediumand contain the functionality of the IEEE 802.11 protocols, for example,including MAC (Medium Access Control), PHY (Physical Layer), andconnections to the wireless media. Typically, IEEE 802.11 protocols areimplemented in the hardware and/or software of a network interface card.

IEEE 802.11 standards also define a Basic Service Set or BSS, which isregarded as a basic building block in WLAN architecture. The BSSconsists of a group of access point stations that communicate with oneanother. In independent BSS, the mobile stations communicate directlywith each other. In an infrastructure BSS, all stations in the BSScommunicate with the access point and no longer communicate directlywith the independent BSS, such that all frames are relayed betweenstations by the access point.

A station could be a laptop PC, handheld device, or an access point(referred herein as “access point” or “AP”). Stations can be mobile,portable, or stationary, and all stations support the IEEE 802.11station services of authentication, de-authentication, privacy, and datadelivery. The MAC layer's primary function is to provide a fairmechanism to control access of shared wireless media. However, prior totransmitting a frame, the MAC layer must gain access to the network,which it does through two different access mechanisms: acontention-based mechanism, called the distributed coordination function(DCF), and a centrally controlled access mechanism, called the pointcoordination function (PCF). The PCF modes allow the implementation of aquality of service (QOS) mechanism, but it is optional and requiresextra interactions in order to negotiate a QOS between the mobileterminal and the AP. The DCF mode, considered the default mode, does notprovide any QOS mechanism. Consequently all stations including the basestation AP in WLAN have the same probability to acquire and to send datawithin the medium. This type of service is referred to as a “besteffort.”

BRIEF DESCRIPTION OF THE DRAWINGS

Certain features of the disclosed technology are set forth in theappended claims. However, the accompanying drawings, which are includedto provide further understanding, illustrate disclosed aspects andtogether with the description serve to explain the principles of thesubject technology. In the drawings:

FIG. 1 illustrates an example wireless communication network in whichsome aspects of the technology can be implemented.

FIG. 2A conceptually illustrates a timing specified by an extendedduration field value configured in accordance with some aspects of thetechnology.

FIG. 2B provides a communication timing diagram graphically illustratingan example chronology of communications between an access point (AP),and a variety of receivers, according to some aspects of the technology.

FIG. 3 illustrates steps of an example process for reducing wirelesscontention, according to some aspects of the technology.

FIG. 4 illustrates example hardware components that can be used toimplement an access point (AP), configured in accordance with someaspects of the technology.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious configurations of the technology and is not intended torepresent the only configurations in which the subject technology can bepracticed. The appended drawings are incorporated herein and constitutea part of the detailed description. The detailed description includesspecific details for the purpose of providing a more thoroughunderstanding of the subject technology. However, it will be clear andapparent that the subject technology is not limited to the specificdetails set forth herein and may be practiced without these details. Insome instances, structures and components are shown in block diagramform in order to avoid obscuring the concepts of the subject technology.

Overview:

The subject disclosure relates to systems and methods for reducingaccess contention and the resultant collisions in a wireless network. Insome aspects, a method or process of the technology includes steps forexchanging data packets with multiple client devices in a wirelessnetwork, and based on the data exchange, identifying a first clientdevice and anticipating transmission of a packet based on informationabout layer 4 (or above) protocols. The method can further include stepsfor broadcasting a Layer 2 packet to the client devices, wherein theLayer 2 packet includes a duration field having an extended durationvalue, configured to suppress transmission by other listening clientdevices, allowing one or more anticipated packets to be received fromthe first client device without contention or collision from the otherclient devices.

Description:

A wireless local area network (WLAN) system works in an unauthorizedspectrum shared by multiple users on a channel. If multipleclient/receiver devices send data at the same time, the transmitted datapackets can interfere, causing a collision. Therefore, in WLAN systems,a carrier sense multiple access with collision avoidance (CSMA/CA)mechanism is used to avoid a collision.

Carrier sense (CS) indicates that: before sending a frame, any deviceconnected to a medium needs to sense the medium, and only when it isdetermined that the medium is idle, can the device can send the frame.Multiple Access (MA) provides that multiple devices can access a mediumat the same time, and a frame sent by one device may also be received bymultiple devices. A working manner of the CSMA/CA mechanism is that whena device intends to send a frame and obtains (by means of sensing) thata channel is idle, after the channel remains idle for a time period, ifthe channel is still idle after the device waits for another random timeperiod (e.g., a “backoff period”), the device submits data. Because awaiting time of each device is generated randomly, it is likely thatthere is a difference, so that a possibility of collision can bereduced. Thus, a probability of a collision is related to how busy asystem is. However, in WLAN systems, there is a “hidden node” problem.That is, when an access point (AP), e.g., “AP1” sends data to a receiverstation (STA), a station that fails to sense AP1 (e.g., AP2), mayconsider the channel to be idle and start to send data, therebyinterfering with a receiving device STA. This problem cannot be fullyresolved by using the CSMA/CA protocol.

Because of the hidden node problem, in the WLAN system, the request tosend (Request to send, RTS)/clear to send (Clear to send, CTS) protocolis generally used to perform transmission protection. Using RTS/CTS achannel is reserved before data is sent. For example, when AP1 sendsdata to STA, AP2 can also perform sending, thereby interfering withreceiving of the STA transmission. However, the RTS/CTS protocolrequires that, before sending data, AP1 first sends an RTS frame, andthe receiving STA returns a CTS frame after receiving the RTS frame. AllAPs or STAs, except the intended recipient, receiving the RTS or CTSframe, set a network allocation vector (Network Allocation Vector, NAV)according to an indication of the received RTS or CTS frame (i.e., a“duration field”), where the NAV is a time corresponding to a sendingtime required by the AP1. These APs or STAs cannot send data within theNAV time. After sending an RTS (Layer 2) frame and receiving a responseof the STA e.g., a CTS indication, AP1 obtains a sending opportunity,and AP1 sends data to the STA within this time period, which is notinterfered with by other nearby APs or STAs.

In many WLAN implementations, the vast majority of data traffic isTCP/IP traffic. In such instances, Layer 4 acknowledgements aretypically sent by the STA a short period after the Layer 4 data isreceived, and outside of the time period protected by the NAV as set bythe transmission of the Layer 4 data. As a result, a large proportion ofwireless contention occurs between multiple different STAs transmissionsof Layer 4 ACKs. This problem is exacerbated when the STAs have poorantennas relative to the AP. For instance if the AP is mounted high upin a stadium, with a high gain antenna, and the STAs are mobile devices,low down in a crowd of people, with a low gain antenna, then the STAsmay be hidden from each other, but not from the AP.

Aspects of the technology resolve the problems of wireless contentioncaused before and/or during issuance of Layer 3/4 acknowledgements by areceiving STA (e.g., TCP ACKs), through the extension of the durationfield until a point in time, before which, the anticipated higher layerresponses or other traffic are received by the AP.

FIG. 1 illustrates an example wireless communication network 100 inwhich some aspects of the technology can be implemented. FIG. 1illustrates an Access Point (AP), configured for wireless communicationwith multiple receivers or client devices (e.g., STA1, STA2, and STA3).It is understood that additional (or fewer) STAs and/or APs could beimplemented in network 100, without departing from the scope of thetechnology.

The AP may have access or interface to a Distribution System (DS) oranother type of wired/wireless network that may carry traffic in and outof a BSS (not illustrated). Thus traffic to STAs can originate fromoutside the BSS, and arrive through the AP for delivery to the STAs.Conversely, traffic originating from STAs to destinations outside theBSS can be sent to the AP to be delivered to the respectivedestinations. Traffic between STAs within the BSS can be sent throughthe AP where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be peer-to-peer traffic.

Using the IEEE 802.11 infrastructure mode of operation, the AP cantransmit on a fixed channel, for example that is 20 MHz wide, anddesignated as the operating channel of the BSS. This channel may also beused by the STAs to establish a connection with the AP. The channelaccess in an IEEE 802.11 system may be Carrier Sense Multiple Accesswith Collision Avoidance (CSMA/CA). In this mode of operation, the STAs,including the AP, can sense the primary channel. If the channel isdetected to be busy, the STA may back off. If the channel is detected tobe free, the STA may acquire the channel and transmit data.

It is understood that network 100 can implement various wirelessstandards using different channel sizes (bandwidths), without departingfrom the technology. By way of example, IEEE 802.11n, High Throughput(HT) STAs may be used, e.g., implementing a 40 MHz communicationchannel. This can be achieved, for example, by combining a primary 20MHz channel, with an adjacent 20 MHz channel to form a 40 MHz widecontiguous channel. In IEEE 802.11a/c, very high throughput (VHT) STAscan also be supported, e.g., 20 MHz, 40 MHz, 80 MHz, and/or 160 MHz widechannels. The 40 MHz, and 80 MHz, channels can be formed, e.g., bycombining contiguous 20 MHz channels. A 160 MHz channel may be formed,for example, by combining eight contiguous 20 MHz channels, or bycombining two non-contiguous 80 MHz channels (e.g., referred to as an80+80 configuration).

Additionally, although several of the examples provided describewireless contention reduction in the context of an 802.11 WLANarchitecture, is understood that other protocols can be implementedwithout departing from the technology. That is, wireless contentionreduction techniques can be implemented in virtually any infrastructuralcontext in which manipulation of an extension field duration (e.g.provided in a Layer 2 packet), is based on expectations of higher layerpacket receipt (e.g., of Layer 3 or 4 packets or TCP/IP ACKs).

In practice, wireless contention between AP1, STA1, STA2, and STA3, canbe reduced by the extension of the 802.11 duration field transmitted byAP1. For example, with respect to example network 100, AP1 can beconfigured to determine a likelihood that Layer 3 or Layer 4 packets areprovided in response to any data transmitted to any of the networkreceivers (e.g., STA1, STA2, and STA3).

Data exchange between AP1 and any (or all) of the receivers in network100 can be used to determine (at AP1), the likelihood of the subsequentreceipt of higher layer responses or other transmissions, such as TCPACKs. Based on the anticipated receipt of higher layer traffic, AP1 canadjust a duration field (e.g., indicated in a RTS frame or anotherframe), used to initiate transfer to any of the receiving STAs (i.e.where the receiver address is that of the receiving STA). The extendedduration field value can be commensurate with a predicted time durationduration necessary for AP1 to receive all potentially inboundanticipated traffic, and complete the TXOP (e.g. subsequent L2 ACK orBlock ACK). As discussed above, by increasing the duration field,wireless contention between STAs (STA1, STA2, STA3) and AP1, can bereduced by suppressing packet transmission by non-participating STAsuntil a full TCP transfer between AP1 and the receiving STA hascompleted.

By way of example, before initiating a data transfer to STA1, AP1 canpredict that a response from STA1 will include Layer 3 and Layer 4traffic. In particular, AP1 can determine the likelihood that STA1'sresponse includes one or more TCP ACK packets, and the timing of whenthose are expected. As discussed in further detail below, thedetermination of the response type provided STA1 can be based on any ofa variety of network observations. By way of example, the prediction canbe based on a history of packet exchange between AP1 and STA1, a historyof data packet exchange between AP1 and one or more nodes similar toSTA1, and/or based on a type of data transferred from AP1 to STA1 (e.g.,voice-over IP traffic), etc. In some aspects, machine-learningapproaches can be implemented, for example, to predict or model theresponse types and/or durations for STA replies to AP1 transfers, basedon dynamic network observations.

After AP1 has determined that subsequent STA1 responses are likely toinclude TCP/IP ACKs, adjustment of the duration is performed to extendthe duration to at least a time necessary for AP1 to receive anysubsequent TCP/IP ACKs, or the time for the anticipated response can bereserved later on by scheduling transmission of a frame to the client,e.g., if the delay is large and other transmissions are available tofill in the time. As such, the frame received by the other STAs innetwork 100 signals that the wireless medium is not available fortransfer (e.g., to STA2, and STA3), until after expiration of the timeperiod indicated by the extended duration field value. Transmissionsuppression of other receivers in network 100 is ended after thisexpiration.

As discussed in further detail below, extension field duration can alsotake consideration of the time required to perform batch datatransmission, e.g., by an AP to a given STA, as well as the expectedbatch receipt of multiple TCP ACKs.

FIG. 2A graphically illustrates timing differences between a wirelessmedium reservation time specified by a standard duration field 214, andthat of a configured (extended) value provide in extended duration field216 of the subject technology. As illustrated, Layer 2 (L2) packetsinclude a RTS packet 204, CTS packet 206, and L2 acknowledgement (ACK)210, and L2 acknowledgement ACK 213. Layer 3/4 (L3/4) response packetsinclude data 208, and L4 ACK 212. As used in the example of FIG. 2A, L4ACK 212 represents one or more TCP/IP ACK/s. However, it is understoodthat LA ACK 212 can represent any packet transmitted on a higher layer(e.g., Layer 3 or 4) in immediate or anticipated response to a lowerlayer (e.g. L2) data transmission.

In practice, RTS 204 is initially broadcast by a transmitting AP, suchas AP1 discussed above. RTS 204 includes an extended duration fieldvalue that indicates an extended time duration for which allnon-recipient receiver nodes (e.g., non-receiving STAs) must wait beforeresuming wireless contention. The intended recipient node, however, ispermitted to respond, e.g., by sending back a “clear to send” (CTS)packet 206.

Subsequent transmission of data by the access point to the intendedreceiver can include the transfer of data packets 208, followed by thereceipt of one or more L2 ACKs 210. Subsequently, one or morehigher-layer packets (e.g., L3/4 ACKs) 212 are received by the receiverand acknowledged with L2 ACK 213, after which the time period specifiedby the extended duration field value expires, permitting other nodes inthe network to begin the process of contention.

It is understood that any of data packet/s 208, L2 ACKs 210, 213, and/orL3/4 ACK/s 212 can represent batch packet transfers. For example, datapacket 208 can represent a stream of packets transmitted from an AP(e.g., AP1), to a designated receiver (e.g., STA1). Similarly, ACKs 212can represent a batch of TCP/IP acknowledgements sent from thedesignated receiver back to the AP. As such, the extended duration value216 specified in the duration field of RTS 204 can be sufficient toaccount for an end-to-end time needed to complete a batch transfer ofdata packets or several batches, and a batch receipt of (TCP/IP)acknowledgement packets, by the AP.

FIG. 2B provides a communication timing diagram 201, graphicallyillustrating an example chronology of communications between an accesspoint, and a variety or receivers, according to some aspects of thetechnology. Timing diagram 201 illustrates a chronology of dataexchanged between Access Point (AP) 218, intended receiver 220, andmultiple other receivers 222 in a wireless network environment. Forsimplicity sake, diagram 201 indicates signaling between transmittingand intended recipient devices. As understood by one of skill in theart, wireless transmissions can be received by any device in thebroadcast range.

In the provided example, AP 218 initially broadcasts an RTS packet 224,which is received by Intended Receiver 220, as well as one or more otherreceivers 222. In accordance with aspects of the disclosed technology,RTS packet 224 includes an extended duration field value 203 calibratedbased on a time period 203 required for AP 218 to receive one or moreLayer 4 acknowledgement packets (ACKs) from Intended Receiver 220. Eachof the non-intended receivers in the network (e.g., Other Receivers222), are silenced for the time period 203 indicated by the extendedduration field value in RTS packet 224. Intended Receiver 220, however,is permitted to transmit, and subsequently issues CTS packet 226 back toAP 218.

Subsequently, AP 218 can transfer a batch of data packets 228 toIntended Receiver 220. In some implementations, each separate packettransferred in batch 228 can precipitate a Layer 2 acknowledgement(e.g., L2 ACK 230) that is issued from Intended Receiver 220.Subsequently, one or more batches of Layer 3 acknowledgements (e.g.,Batch TCP ACK 232), can be transmitted from Intended Receiver 220 toAccess Point 218. In some approaches, TCP/IP ACKs are provided for everyother data packet in batch 228. However, Layer 4 ACKs can be provided ona more (or less) frequent basis, without deviating from the scope of thetechnology.

In some implementations, Intended Receiver 220 may send an optional RTS231 to AP 218, e.g., before transmission of the Batch TCP ACK 232. It isunderstood that wireless broadcasts can be received by each device inthe wireless network; however, the illustration of FIG. 2B illustratesonly intended recipients of broadcasts by each device.

By extending the duration field indicated in the RTS packet (e.g., RTS224), until all anticipated Layer 4 acknowledgements have been receivedand acknowledged at L2, wireless contentions that would have occurredjust after issuance of the L2 ACK 230 are eliminated.

FIG. 3 illustrates steps of an example process 300 for reducing wirelesscontention, according to some aspects of the technology. Process 300begins with step 302 in which a multitude of packets are exchanged(e.g., by an access point), with a plurality of devices (receivers/STAs)in a wireless network. As indicated above, the provided examples aredescribed in the context of 802.11 wireless network implementations.However, other protocols can be used, without departing from thetechnology.

In some aspects, the exchange of packets with one or more devices in thewireless network can be used as an opportunity for the AP to “learn”about the type of packets transacted with one or more nodes in anetwork. The AP can be configured to inspect packets originating fromdifferent receivers in the network, for example, to determine thepresence of Layer 2, Layer 3, and/or Layer 4 packets. In some aspects,traffic types can be identified based on a regularity of packetsreceived from and/or transmitted to a particular receiver. By way ofexample, a high regularity of packet exchange may indicate a particulartraffic flow type, such as, voice over IP (VoIP), which corresponds totransfers associated with a specific packet layer. In VoIP flows, thetraffic from the STA can be reliably anticipated since it follows aconstant pattern. By delaying the traffic from the AP to the STA untiljust before the regular transmission from the STA to the AP happens, thetraffic can have it's duration field extended to cover the transmissionsof VoIP from the STA to the AP, thus avoiding any contention by the STAfor this traffic.

In some aspects, the AP can be configured to monitor traffic flows, e.g.using a machine learning model, to identify one or more nodes in thewireless network (e.g. identify a first client device), from whichsubsequent Layer 3 and/or Layer 4 packets are likely to be received(step 304). In some aspects, the AP can also be configured to predictduration necessary to send a batch of data packets to the first clientdevice, and to subsequently receive one or more Layer 4 acknowledgments(e.g., a batch of TCP ACKs). As discussed above, such predictions can beused by the AP to configure a duration specified in a duration field,and used to prevent wireless contention by other network nodes.

Subsequently, at step 306, a Layer 2 packet is provided to the pluralityof client devices (receivers) in the network, which includes theextended duration field value configured in step 304. With the exceptionof the intended receiving node (e.g., the first client device), receiptof the Layer 2 (RTS) packet by every other node in the network causesthe respective receiving nodes to set their virtual carrier sense, andthus to avoid wireless contention for the specified duration. Becausethe duration is based on an amount of time needed for the AP to completethe reception and 802.11 acknowledgement of all TCP ACKs, a significantamount of wireless contention in the network is avoided.

FIG. 4 illustrates an example network device 410 that can be used toimplement an access point or one or more client devices, as discussedabove. Network device 410 includes a master central processing unit(CPU) 462, interfaces 468, and a bus 415 (e.g., a PCI bus). When actingunder the control of appropriate software or firmware, the CPU 462 canbe configured to carry out a process for reducing contention in awireless medium, in accordance with some aspects of the technology.

For example, CPU 432 can be configured to facilitate implementation ofdata packet exchange with a plurality of client devices in a wirelessnetwork, and based on the exchange, identify a first device from among aplurality of client devices from which one or more higher-layer packetsare likely to be received. In some aspects, CPU 432 can be configured totransmit (e.g., via a transceiver portion of interfaces 468), a packetto a first device, wherein the packet includes an extended durationfield value, and is configured to be received by one or more of theplurality of devices and to suppress transmission by the one or more ofthe plurality of devices until at least one of the higher-layer packetsare received from the first device.

The CPU 462 preferably accomplishes all these functions under thecontrol of software including an operating system and any appropriateapplications software. CPU 462 may include one or more processors 463such as a processor from the Motorola family of microprocessors or theMIPS family of microprocessors. In an alternative embodiment, processor463 is specially designed hardware for controlling the operations ofrouter 410. In a specific embodiment, a memory 461 (such as non-volatileRAM and/or ROM) also forms part of CPU 462. However, there are manydifferent ways in which memory could be coupled to the system.

Interfaces 468 are typically provided as interface cards (sometimesreferred to as “line cards”). Generally, they control the sending andreceiving of data packets over the network and sometimes support otherperipherals used with the router 410. Among the interfaces that may beprovided are Ethernet interfaces, frame relay interfaces, cableinterfaces, DSL interfaces, token ring interfaces, and the like. Inaddition, various very high-speed interfaces may be provided such asfast token ring interfaces, wireless interfaces, Ethernet interfaces,Gigabit Ethernet interfaces, ATM interfaces, HSSI interfaces, POSinterfaces, FDDI interfaces and the like. Generally, these interfacesmay include ports appropriate for communication with the appropriatemedia. In some cases, they may also include an independent processorand, in some instances, volatile RAM. The independent processors maycontrol such communications intensive tasks as packet switching, mediacontrol and management. By providing separate processors for thecommunications intensive tasks, these interfaces allow the mastermicroprocessor 462 to efficiently perform routing computations, networkdiagnostics, security functions, etc.

Although the system shown in FIG. 4 is one specific network device ofthe present invention, it is by no means the only network devicearchitecture on which the present invention can be implemented. Forexample, an architecture having a single processor that handlescommunications as well as routing computations, etc. is often used.Further, other types of interfaces and media could also be used with therouter.

Regardless of the network device's configuration, it may employ one ormore memories or memory modules (including memory 461) configured tostore program instructions for the general-purpose network operationsand mechanisms for roaming, route optimization and routing functionsdescribed herein. The program instructions may control the operation ofan operating system and/or one or more applications, for example. Thememory or memories may also be configured to store tables such asmobility binding, registration, and association tables, etc.

It is understood that any specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged, or that only aportion of the illustrated steps be performed. Some of the steps may beperformed simultaneously. For example, in certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the embodiments describedabove should not be understood as requiring such separation in allembodiments, and it should be understood that the described programcomponents and systems can generally be integrated together in a singlesoftware product or packaged into multiple software products.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.”

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as a “configuration” does not imply that suchconfiguration is essential to the subject technology or that suchconfiguration applies to all configurations of the subject technology. Adisclosure relating to a configuration may apply to all configurations,or one or more configurations. A phrase such as a configuration mayrefer to one or more configurations and vice versa.

The word “exemplary” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs.

What is claimed is:
 1. A system for reducing access contention for dataexchange in a wireless medium, comprising: one or more processors; anetwork interface coupled to the one or more processors; and atransceiver coupled to the one or more processors, and wherein theprocessors are configured to perform operations comprising: exchanging,via the transceiver, data packets with a plurality of client devices ina wireless network; based on the exchanging of the data packets,identifying a first device from among the plurality of client devicesfrom which one or more higher-layer packets are likely to be received;and transmitting, via the transceiver, a packet to the first device,wherein the packet transmitted to the first device comprises an extendedduration field value, and wherein the packet transmitted to the firstdevice is configured to be received by one or more of the plurality ofdevices and to suppress transmission by the one or more of the pluralityof devices until at least one of the higher-layer packets are receivedfrom the first device.
 2. The system of claim 1, wherein the packetcomprises a Request to Send (RTS) frame formatted based on an 802.11wireless networking protocol, and wherein the RTS frame contains theextended duration field value.
 3. The system of claim 1, wherein atleast one of the higher-layer packets comprises a Transmission ControlProtocol (TCP) acknowledgement (ACK) packet.
 4. The system of claim 1,wherein the extended duration field value is configured to suppresstransmission by one or more of the plurality of client devices until atime duration necessary to receive a Clear to Send (CTS) packet,transmit a plurality of data packets to the first device, and receive aplurality of Transmission Control Protocol (TCP) acknowledgement (ACK)packets from the first device.
 5. The system of claim 1, wherein theextended duration field value is determined based on a number of datapackets to be transmitted to the first device.
 6. The system of claim 1,wherein, identifying a first device from among the plurality of clientdevices for which one or more higher-layer packets are likely to bereceived, further comprises: identifying a traffic type for one or morepackets previously received from the first device; and determining alikelihood that future packets received from the first device willcontain higher-layer traffic based on the traffic type for the one ormore packets previously received from the first device.
 7. The system ofclaim 1, wherein, identifying a first device from among the plurality ofclient devices for which one or more higher-layer packets are likely tobe received, further comprises: identifying a traffic type for one ormore packets previously received from the one or more of the pluralityof client devices, wherein the one or more of the plurality of clientdevices are different from the first client device; and determining alikelihood that future packets received from the first device willcontain higher-layer traffic based on the traffic type for the one ormore packets previously received from the one or more of the pluralityof client devices.
 8. A computer-implemented method for reducing accesscontention a wireless medium, comprising: exchanging data packets with aplurality of client devices in a wireless network; based on theexchanging of the data packets, identifying a first device from amongthe plurality of client devices from which one or more higher-layerpackets are likely to be received; and transmitting a packet to thefirst device, wherein the packet transmitted to the first devicecomprises an extended duration field value, and wherein the packettransmitted to the first device is configured to be received by one ormore of the plurality of devices and to suppress transmission by the oneor more of the plurality of devices until at least one of thehigher-layer packets are received from the first device.
 9. Thecomputer-implemented method of claim 8, wherein the packet comprises aRequest to Send (RTS) frame formatted based on an 802.11 wirelessnetworking protocol, and wherein the RTS frame contains the extendedduration field value.
 10. The computer-implemented method of claim 8,wherein at least one of the higher-layer packets comprises aTransmission Control Protocol (TCP) acknowledgement (ACK) packet. 11.The computer-implemented method of claim 8, wherein the extendedduration field value is configured to suppress transmission by one ormore of the plurality of client devices until a time duration necessaryto receive a Clear to Send (CTS) packet, transmit a plurality of datapackets to the first device, and receive a plurality of TransmissionControl Protocol (TCP) acknowledgement (ACK) packets from the firstdevice.
 12. The computer-implemented method of claim 8, wherein theextended duration field value is determined based on a number of datapackets to be transmitted to the first device.
 13. Thecomputer-implemented method of claim 8, wherein, identifying a firstdevice from among the plurality of client devices for which one or morehigher-layer packets are likely to be received, further comprises:identifying a traffic type for one or more packets previously receivedfrom the first device; and determining a likelihood that future packetsreceived from the first device will contain higher-layer traffic basedon the traffic type for the one or more packets previously received fromthe first device.
 14. The computer-implemented method of claim 8,wherein, identifying a first device from among the plurality of clientdevices for which one or more higher-layer packets are likely to bereceived, further comprises: identifying a traffic type for one or morepackets previously received from the one or more of the plurality ofclient devices, wherein the one or more of the plurality of clientdevices are different from the first client device; and determining alikelihood that future packets received from the first client devicewill contain higher-layer traffic based on the traffic type for the oneor more packets previously received from the one or more of theplurality of client devices.
 15. A non-transitory computer-readablestorage medium comprising instructions stored therein, which whenexecuted by one or more processors, cause the processors to performoperations comprising: exchanging data packets with a plurality ofclient devices in a wireless network; based on the exchanging of thedata packets, identifying a first device from among the plurality ofclient devices from which one or more higher-layer packets are likely tobe received; and transmitting a packet to the first device, wherein thepacket transmitted to the first device comprises an extended durationfield value, and wherein the packet transmitted to the first device isconfigured to be received by one or more of the plurality of devices andto suppress transmission by the one or more of the plurality of devicesuntil at least one of the higher-layer packets are received from thefirst device.
 16. The non-transitory computer-readable storage medium ofclaim 15, wherein the packet comprises a Request to Send (RTS) frameformatted based on an 802.11 wireless networking protocol, and whereinthe RTS frame contains the extended duration field value.
 17. Thenon-transitory computer-readable storage medium of claim 15, wherein atleast one of the higher-layer packets comprises a Transmission ControlProtocol (TCP) acknowledgement (ACK) packet.
 18. The non-transitorycomputer-readable storage medium of claim 15, wherein the extendedduration field value is configured to suppress transmission by one ormore of the plurality of client devices until a time duration necessaryto receive a Clear to Send (CTS) packet, transmit a plurality of datapackets to the first device, and receive a plurality of TransmissionControl Protocol (TCP) acknowledgement (ACK) packets from the firstdevice.
 19. The non-transitory computer-readable storage medium of claim15, wherein the extended duration field value is determined based on anumber of data packets to be transmitted to the first device.
 20. Thenon-transitory computer-readable storage medium of claim 15, wherein,identifying a first device from among the plurality of client devicesfor which one or more higher-layer packets are likely to be received,further comprises: identifying a traffic type for one or more packetspreviously received from the first device; and determining a likelihoodthat future packets received from the first device will containhigher-layer traffic based on the traffic type for the one or morepackets previously received from the first device.